Liao Junpeng, Huang Dongmei, Lu Yegang, Li Yan, Tian Ye
Ningbo University, Ningbo, China.
Hong Kong Polytechnic University, Hong Kong SAR, China.
Nanophotonics. 2024 Aug 30;13(22):4137-4148. doi: 10.1515/nanoph-2024-0301. eCollection 2024 Sep.
Mode converters (MCs) play an essential role in mode-division multiplexing (MDM) systems. Numerous schemes have been developed on the silicon-on-insulator (SOI) platform, yet most of them focus solely on the conversion of fundamental mode to one or two specific higher-order modes. In this study, we introduce a hybrid shape optimization (HSO) method that combines particle swarm optimization (PSO) with adjoint methods to optimize the shape of the S-bend waveguide, facilitating the design of arbitrary-order MCs featuring compactness and high performance. Our approach was validated by designing a series of 13 μm-long MCs, enabling efficient conversion between various TE modes, ranging from TE to TE. These devices can be fabricated in a single lithography step and exhibit robust fabrication tolerances. Experiment results indicate that these converters achieve low insertion losses under 1 dB and crosstalks below -15 dB across bandwidths of 80 nm (TE-TE), 62 nm (TE-TE), 70 nm (TE-TE), 80 nm (TE-TE), 55 nm (TE-TE), and 75 nm (TE-TE). This advancement paves the way for flexible mode conversion, significantly enhancing the versatility of on-chip MDM technologies.
模式转换器（MCs）在模式分割复用（MDM）系统中起着至关重要的作用。在绝缘体上硅（SOI）平台上已经开发了许多方案，但其中大多数仅专注于将基模转换为一两种特定的高阶模式。在本研究中，我们引入了一种混合形状优化（HSO）方法，该方法将粒子群优化（PSO）与伴随方法相结合，以优化S形弯曲波导的形状，从而便于设计具有紧凑性和高性能的任意阶MCs。我们的方法通过设计一系列13μm长的MCs得到验证，能够在从TE到TE的各种TE模式之间实现高效转换。这些器件可以在单个光刻步骤中制造，并且具有很强的制造容差。实验结果表明，这些转换器在80nm（TE-TE）、62nm（TE-TE）、70nm（TE-TE）、80nm（TE-TE）、55nm（TE-TE）和75nm（TE-TE）的带宽内实现了低于1dB的低插入损耗和低于-15dB的串扰。这一进展为灵活的模式转换铺平了道路，显著提高了片上MDM技术的通用性。
